George Wendt, founder and owner of OARS rafting company, recalls a day 48 years ago when a mud and rock slide changed Warm Springs Rapid (in the background) forever.

Any multiday float trip down a large Western river — even one involving naturalists, water policy experts and journalists — is first and foremost an adventure, one with a modicum of danger involved.

In Yampa Canyon, no one, not even the professional guides, approaches the rapid known as Warm Springs without an awareness that lives are at risk where the river’s flow is squeezed through a bottleneck against a sheer 1,600-foot cliff. The drop in the river bed, the compressed waves and one raft-eating hole situated in the middle of the rapid’s wave train can conspire to create havoc. One party from Steamboat Springs that floated through Warm Springs near the peak flow in June saw three of its rafts flip.

No one was injured, and it’s a safe bet that no one took their safety for granted.

The anxiety at Warm Springs this year stemmed from the fact it was not the same rapid that anyone in the party could remember. That’s because in late June or early July 2012, when the river was at near record-low flows, a massive slab of rock peeled off the canyon wall from high above and slammed into the riverbed, leaving behind a large crater and numerous boulders. The large rocks threatened to block access to a safe route around the hole known as Maytag because it has the power to latch onto a heavily-laden raft and trap it in the spin cycle.

By June 9 of 2013, Warm Springs still looked powerful, but the altered rapid was more of an intellectual puzzle to solve than an intimidating monster.

The last time Warm Springs underwent changes of this magnitude was in 1965, and the circumstances were very different.

George Wendt, the 71-year-old founder of the OARS rafting company, which served as outfitter for the 2013 Yampa River Awareness Project expedition, was an eyewitness to the massive debris slide that momentarily dammed the river and ultimately claimed a life 48 years ago.

Wendt recalls the day in 1965 when the famed Warm Springs rapid was drastically changed after heavy rains saturated soils in a side ravine and sent muck and boulders surging into the main channel.

“There were so many stones, and some of them were the size of Volkswagens, it created a dam on the river that lasted for 30 seconds to 2 minutes,” Wendt remembered. “The water level below the dam dropped as if it had been sucked away by a big tsunami.’”

Wendt related how he and some companions had stopped by the rapid to get out of persistent rain.

“It rained hard for between 24 and 26 hours,” Wendt recalled. The men had been floating in a 13-foot military surplus life raft. The thin soils in the canyon had liquified and a thick mixture was flowing down a side gulch until a rock slide dammed it. The pressure of the mud and rock built up until it finally blew out.

Wendt took just enough time to latch onto the boat and, with the help of others, dragged it well up the bank.

Suddenly, the debris dam let go with a roar, and the rapid was changed forever.

The explorers had been visiting a stone pioneer cabin hours earlier, and after the slide, no trace of the structure could be found, Wendt said.

Wendt’s party remained on the bank and watched as the next party of rafters approached. Fortunately, that group noticed the new bathtub ring on the sheer canyon walls and wisely pulled over to scout the newly rearranged rapid. However, the second party, led by commercial guides, proceeded ahead and one of the guides was not wearing a personal floatation device.

“The raft flipped, he fell out and was not seen again,” Wendt recalled.

One thing that is certain about Yampa Canyon and its tributaries is that large rock slides will continually alter the flow of the river that over many thousands of years has cut through the layers of sandstone.

Since the June 7 to 11 float trip passed by, a new rockfall came thundering into Jones Creek above the Jones Hole Campground, sending a party of fishermen scrambling for their lives.

The incident serves as a reminder of how wild and unpredictable Yampa Canyon is.